perf(library/unifier): do not explore branches that will trigger type errors
perf(library/unifier): do not explore branches that will trigger type errors

Signed-off-by: Leonardo de Moura <7610bae85f2b530654cc716772f1fe653373e892@microsoft.com>

rlewis1988/lean,javra/lean,UlrikBuchholtz/lean,fgdorais/lean,c-cube/lean,UlrikBuchholtz/lean,sp3ctum/lean,avigad/lean,eigengrau/lean,leanprover-community/lean,rlewis1988/lean,digama0/lean,soonhokong/lean-windows,soonhokong/lean-osx,leodemoura/lean,leanprover/lean,htzh/lean,fpvandoorn/lean,leanprover-community/lean,htzh/lean,sp3ctum/lean,fpvandoorn/lean2,fpvandoorn/lean,htzh/lean,johoelzl/lean,Kha/lean,fpvandoorn/lean2,leanprover-community/lean,leanprover/lean,digama0/lean,levnach/lean,soonhokong/lean-windows,leodemoura/lean,eigengrau/lean,c-cube/lean,Kha/lean,UlrikBuchholtz/lean,levnach/lean,c-cube/lean,dselsam/lean,UlrikBuchholtz/lean,eigengrau/lean,dselsam/lean,johoelzl/lean,javra/lean,soonhokong/lean-osx,leanprover/lean,eigengrau/lean,soonhokong/lean,rlewis1988/lean,htzh/lean,sp3ctum/lean,Kha/lean,fpvandoorn/lean2,fgdorais/lean,leanprover-community/lean,UlrikBuchholtz/lean,c-cube/lean,fgdorais/lean,javra/lean,fpvandoorn/lean2,levnach/lean,fpvandoorn/lean,dselsam/lean,Kha/lean,avigad/lean,javra/lean,leodemoura/lean,leanprover/lean,dselsam/lean,soonhokong/lean-windows,digama0/lean,Kha/lean,leanprover-community/lean,leodemoura/lean,fpvandoorn/lean2,soonhokong/lean-windows,leanprover-community/lean,javra/lean,leanprover/lean,soonhokong/lean-windows,soonhokong/lean,soonhokong/lean-osx,soonhokong/lean-osx,fpvandoorn/lean,fgdorais/lean,fpvandoorn/lean,leodemoura/lean,levnach/lean,avigad/lean,johoelzl/lean,avigad/lean,rlewis1988/lean,johoelzl/lean,dselsam/lean,soonhokong/lean,fpvandoorn/lean,sp3ctum/lean,avigad/lean,levnach/lean,leodemoura/lean,leanprover/lean,johoelzl/lean,eigengrau/lean,fgdorais/lean,htzh/lean,digama0/lean,soonhokong/lean,fgdorais/lean,johoelzl/lean,avigad/lean,rlewis1988/lean,soonhokong/lean-osx,sp3ctum/lean,rlewis1988/lean,digama0/lean,Kha/lean,soonhokong/lean,digama0/lean,c-cube/lean,dselsam/lean